This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A207955 #9 Jul 22 2025 21:02:59 %S A207955 2,16,102,989,15839,454223,22743106,1965912435,292568573966, %T A207955 74527048580258,32449227184884623,24089588153258657647, %U A207955 30462508808101945246072,65556106479277551484530086 %N A207955 Number of n X n 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 0 1 and 1 0 0 vertically. %C A207955 Diagonal of A207960 %H A207955 R. H. Hardin, <a href="/A207955/b207955.txt">Table of n, a(n) for n = 1..17</a> %e A207955 Some solutions for n=4 %e A207955 ..1..1..0..0....0..1..1..1....1..1..1..0....0..0..1..1....1..0..0..1 %e A207955 ..1..1..0..0....0..1..0..0....0..1..1..0....0..1..1..0....0..0..1..1 %e A207955 ..1..1..0..0....0..0..1..1....1..1..1..0....0..1..1..1....1..0..0..1 %e A207955 ..0..1..0..0....0..1..0..0....1..1..1..0....0..0..1..1....0..0..1..1 %K A207955 nonn %O A207955 1,1 %A A207955 _R. H. Hardin_ Feb 21 2012